Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
  • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
  • A61F2/02—Prostheses implantable into the body
  • A61F2/30—Joints
  • A61F2/32—Joints for the hip
  • A61F2/36—Femoral heads ; Femoral endoprostheses
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
  • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
  • A61F2/02—Prostheses implantable into the body
  • A61F2/30—Joints
  • A61F2/30767—Special external or bone-contacting surface, e.g. coating for improving bone ingrowth
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
  • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
  • A61F2/02—Prostheses implantable into the body
  • A61F2/30—Joints
  • A61F2/30767—Special external or bone-contacting surface, e.g. coating for improving bone ingrowth
  • A61F2/30907—Nets or sleeves applied to surface of prostheses or in cement
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
  • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
  • A61F2/02—Prostheses implantable into the body
  • A61F2/30—Joints
  • A61F2002/30001—Additional features of subject-matter classified in A61F2/28, A61F2/30 and subgroups thereof
  • A61F2002/30316—The prosthesis having different structural features at different locations within the same prosthesis; Connections between prosthetic parts; Special structural features of bone or joint prostheses not otherwise provided for
  • A61F2002/30535—Special structural features of bone or joint prostheses not otherwise provided for
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
  • A61F2250/00—Special features of prostheses classified in groups A61F2/00 - A61F2/26 or A61F2/82 or A61F9/00 or A61F11/00 or subgroups thereof
  • A61F2250/0058—Additional features; Implant or prostheses properties not otherwise provided for

Definitions

• the present invention relates to a prosthetic hip stem for implantation in the femur as a component of a prosthetic hip joint. More particularly, the present invention relates to a prosthetic hip stem having a fully porous coating and a contoured neck portion.
• Orthopedic implants are commonly used to replace some or all of a patient's hip joint in order to restore the use of the hip joint, or to increase the use of the hip joint, following deterioration due to aging or illness, or injury due to trauma.
• a femoral component is used to replace a portion of the patient's femur, including the femoral neck and head.
• the femoral component is typically a hip stem, which includes a stem portion positioned within the prepared femoral canal of the patient's femur and secured via bone cement, or by a press-fit followed by bony ingrowth of the surrounding tissue into a porous coating of the stem portion.
• the hip stem also includes a neck portion adapted to receive a prosthetic femoral head.
• the femoral head is received within a prosthetic acetabular component, such as an acetabular cup received within the prepared recess of the patient's acetabulum.
• One known hip stem includes a core formed of either a cobalt-chromium- molybdenum alloy or titanium, and a porous surface layer in the form of a matrix of small metallic beads or a wire mesh.
• the porous surface layer is sintered to the core by heating the core and the porous surface layer to a high temperature in order to cause the porous surface layer and core to fuse, melt, or bond together along their interface.
• U.S. Patent Nos. 6,395,327, 6,514,288, and 6,685,987 each assigned to the assignee of the present invention and hereby incorporated by reference, disclose various methods of enhancing the fatigue strength and the connection between the core and the porous surface layer of the foregoing types of hip stems.
• the present invention provides a prosthetic hip stem for use in a prosthetic hip joint.
• the hip stem generally includes a core having a stem portion and a neck portion, a polymer matrix layer substantially covering the stem portion of the core, and a porous metal layer substantially covering the polymer matrix layer.
• the polymer matrix layer connects the core and the porous metal layer, and may be injection molded therebetween.
• the neck portion of the hip stem has a relatively thin or slender profile which allows for an increased degree of articulating movement of the hip stem with respect to the acetabular component of a prosthetic hip joint.
• the neck portion of the hip stem additionally includes a version indicator element, such as a bump or a protrusion, which may be tactilely felt by a surgeon to aid the surgeon in positioning the hip stem during a minimally invasive total hip arthroplasty procedure, for example, where direct visualization of the hip stem by the surgeon may not be possible.
• a version indicator element such as a bump or a protrusion
• the core of the hip stem includes grooves, ridges, flats, dimples or other features to enhance the mechanical interconnection between the core and the polymer matrix layer.
• the present invention provides a prosthetic hip stem for implantation into bone including a core including a stem portion and a neck portion, the core including at least one of a recess feature and a protrusion feature; a polymer matrix layer substantially covering the stem portion, the polymer matrix layer cooperatively engaging the at least one of a recess feature and a protrusion feature; and a porous metal layer substantially covering the polymer matrix layer.
• the present invention provides a prosthetic hip stem for implantation into bone including a core including a stem portion and a neck portion, the neck portion terminating in a tapered femoral head fitting having a maximum diameter, wherein a substantial portion of the neck portion is contoured to have a lesser diameter than the maximum diameter of the femoral head fitting.
• the present invention provides a prosthetic hip stem for implantation into bone including a stem portion; a neck portion extending from the stem portion and having a lateral side and a medial side, the medial side including a version indicator element.
• Fig. 1 is a first isometric view of a hip stem according to the present invention
• Fig. 2 is a second isometric view of the hip stem of Fig. 1;
• Fig. 3 is a first isometric view of the core of the hip stem of Figs. 1 and 2;
• Fig. 4 is a second isometric view of the core of the hip stem of Figs. 1 and 2;
• Fig. 5 is a sectional view through the hip stem, taken along line 5-5 of Fig. 2;
• Fig. 6 is a side view of the proximal end of the hip stem, showing the contoured neck portion and the version indicator feature;
• Fig. 7 is an isometric view of the proximal end of the hip stem, showing the contoured neck portion;
• FIG. 8 is a side view of the proximal end of the hip stem, shown with a femoral head thereof fitted within an acetabular cup which is in turn positioned within an acetabulum, and illustrating the relatively large degree of articulating movement possible therebetween;
• Fig. 9 is a schematic top view of the hip stem, showing relative neutral and ante version positions of the hip stem with respect to a patient in solid and dashed lines, respectively;
• Fig. 10 is an isometric view of the proximal end of the core of the hip stem, showing the curved groove therein;
• Fig. 11 is an isometric view of a portion of the distal end of the core of the hip stem, showing the distal boss of the core, including a plurality of dimples around the boss and a plurality of ridges in the stem portion of the core.
• a prosthetic hip stem 20 which generally includes stem portion 22, and neck portion 24 extending at a generally obtuse angle from stem portion 22 and including a tapered femoral head fitting 26.
• Stem portion 22 of hip stem 20 is received within a prepared femoral canal of a patient's femur to anchor hip stem 20 within the patient's femur.
• a femoral head component is fitted on femoral head fitting 26, and is in turn received within a prosthetic acetabular component, such as an acetabular cup seated within a prepared recess in the patient's acetabulum, to thereby provide an articulating, prosthetic hip joint.
• Hip stem 20 further defines proximal end 28, distal end 30, lateral side 32, medial side 34, as well as opposing anterior and posterior sides depending upon whether hip stem 20 is used with a patient's right or left femur.
• hip stem 20 generally includes a substrate or core 36 generally defining stem portion 22 and neck portion 24 and, as best seen in Fig. 5, a polymer matrix layer 38 substantially covering stem portion 22 of core 36, and a porous metal layer 40 substantially covering polymer matrix layer 38.
• Polymer matrix layer 38 and porous metal layer 40 may cover substantially all of stem portion 22 of core 36, or alternatively, may cover only selected portions thereof, as desired.
• stem portion 22 has a length L (Fig. 1) extending generally from proximal end 28 to distal end 30, and, in one embodiment, stops slightly short of each end 28, 30 by approximately 0.3 inches.
• Porous metal layer 40 extends along length L from approximately 10, 20, 30% thereof or as much as 70, 80, 90, or 95% thereof. In one embodiment, porous metal layer 40 extends along stem portion 22 for approximately 33% of the length thereof. In another embodiment, porous metal layer 40 covers approximately 33% of proximal end 28 of stem portion 22, i.e., a midcoat porous stem.
• Core 36 may be made from a cobalt-chromium-molybdenum alloy or a titanium alloy, for example, via a forging or casting process, followed by machining to achieve a desired shape or profile.
• Polymer matrix layer 38 may be formed of an inert polyaryletherketone (“PAEK”) polymer such as, for example, polyetheretherketone (“PEEK”).
• PAEK polyaryletherketone
• Porous metal layer 40 may be a metal wire mesh of titanium fibers, or alternatively, may also comprise a metal bead matrix or other porous metal structures produced in accordance with Trabecular MetalTM technology of Zimmer, Inc. of Warsaw, Indiana, for example.
• Hip stem 20 may be manufactured as follows. First, core 36 is forged, followed by machining core 36 after forging to form a desired shape or profile for core 36. Core 36 is then grit blasted to sufficiently roughen its surface, and then is heat treated to facilitate polymer flow across core 36 during the injection molding process. Thereafter, core 36 is positioned within an injection molding machine with stem portion 22 of core 36 positioned within porous metal layer 40, with a gap provided therebetween. Thereafter, polymer matrix layer 38 is injected into the space between core 36 and porous metal layer 40 through suitable gates, with polymer matrix layer 38 permeating into porous metal layer 40 and into the surface of stem portion 22 of core 36 via grooves 52, dimples 56, ridges 58, and/or flats 60.
• porous metal layer 40 Upon cooling of polymer matrix layer 38, porous metal layer 40 is firmly bonded or secured to stem portion 22 of core 36.
• core 36 is not subjected to a sintering process to apply porous metal layer 40, thereby maintaining the fatigue strength of core 36.
• neck portion 24 of hip stem 20 is contoured to allow for increased articulating movement of hip stem 20 with respect to an acetabular component in a prosthetic hip joint, as illustrated in Fig. 8.
• neck portion 24 of hip stem 20 includes a neck section 42 which extends between stem portion 22 and femoral head fitting 26.
• Neck section 42 is shaped with a relatively thin or slender profile, having a diameter along a substantial portion thereof which is less than the maximum diameter of femoral head fitting 26.
• neck section 42 may include a plurality of scalloped recesses 44 therearound which may be formed by removal of material from the original forging of core 36 by machining. As shown in Fig.
• neck section 42 allows for an increased degree of angular, articulating movement of hip stem 20 with respect to the acetabular component in a prosthetic hip joint when a prosthetic femoral head 43 is fitted on fitting 26 of stem 20 and received within the acetabular component, which is shown in Fig. 8 as an acetabular cup 46 positioned within a prepared recess in the surrounding acetabulum.
• neck portion 24 of core 36 of hip stem 20 may include an instrument engagement fitting 47 in proximal end 28 thereof within which an instrument (not shown) may be engaged to aid in driving hip stem 20 into the prepared femoral canal of a patient's femur.
• neck portion 24 of hip stem 20 also includes a version indicator feature 48, which is shown herein as a bump or protrusion 50 projecting from medial side 34 of neck portion 24 of hip stem 20.
• version indicator feature 48 is a tactile feature on hip stem 20 which may be felt by a surgeon during implantation of hip stem 20 to aid the surgeon in positioning hip stem 20 according to a desired version or alignment.
• U.S. Patent No. 6,676,706, assigned to the assignee of the present invention and incorporated herein by reference, discloses a method for performing a "non-open", or minimally invasive, total hip arthroplasty.
• a small anterior incision is made for preparing a recess or seat in the acetabulum for receiving an acetabular cup, which is inserted and positioned within the acetabulum through the anterior incision.
• a small posterior incision is also made for preparing the femur and for receiving a hip stem, such as hip stem 20, which is positioned within the prepared femoral canal of the femur.
• hip stem such as hip stem 20
• a surgeon may feel protrusion 50 of version indicator element 48 by inserting the surgeon's fingers through the anterior incision, for example, to position hip stem 20 in an anteversion alignment, shown in dashed lines in Fig. 9, in which neck portion 24 of hip stem 20 is rotated approximately 12° to 14° anteriorly with respect to stem portion 22 from the neutral version, or direct medial-lateral, alignment shown in solid lines in Fig. 9.
• the surgeon may tactilely align protrusion 50 of version indicator element 48 with respect to one or more grooves which are cut in the medial calcar of the prepared femur in order to position hip stem 20.
• Protrusion 50 of version indicator element 48 may also be used by the surgeon to position hip stem 20 in a position other than in an anteversion alignment if needed.
• protrusion 50 of version indicator element 48 advantageously allows the surgeon to position hip stem 20 according to a desired alignment during a minimally invasive hip arthroplasty procedure without direct visualization of hip stem 20.
• version indicator feature 48 is shown herein as bump or protrusion
• tactile elements such as a recess, a group of recesses, or a ridge or a group of ridges, for example, in medial side 34 of neck portion 24 of hip stem 20, or at another location or locations on neck portion 24 of hip stem 20.
• core 36 includes a plurality of features for enhancing the mechanical interconnection between core 36 and polymer matrix layer 38.
• proximal end 28 of stem portion 22 of core 36 includes a curved, generally "candy cane"-shaped or “number 7"-shaped groove 52 on one or both of the anterior and posterior sides thereof.
• the material of polymer matrix layer 38 is injected into the space between core 36 and porous metal layer 40, the material of polymer matrix layer 38 flows into and substantially fills grooves 52 to fo ⁇ n a robust mechanical interconnection between core 36 and polymer matrix layer 38 upon curing of the material.
• the mechanical interconnection resists relative movement between core 36 and polymer matrix layer 38, such as rotational movement, responsive to torsional and/or other types of loading which may be imposed upon core 36 when hip stem 20 is used in a hip joint, and in particular, after porous metal layer 40 becomes substantially fused to the surrounding femoral bone tissue.
• distal end 30 of core 36 includes a boss 54 which provides a rigid leading surface for insertion of hip stem 20 into a prepared femoral canal.
• Boss 54 also includes a plurality of dimples 56 formed circumferentially therearound.
• the material of polymer matrix layer 38 flows into and substantially fills dimples 56 to form a robust mechanical interconnection between core 36 and polymer matrix layer 38 upon curing of the material.
• the mechanical interconnection also resists relative movement, such as relative rotational movement, between core 36 and polymer matrix layer 38 responsive to torsional and/or other types of loading upon core 36 after hip stem 20 is implanted.
• stem portion 22 of core 36 may additionally include further features to enhance the mechanical interconnection between core 36 and polymer matrix layer 38, such as ridges 58 and/or flats 60, or other projecting or recessed features in core 36 such as grooves, cavities, bores, dimples, bumps, protuberances, protrusions, or other features which may be formed in core 36 by forging or post-forging machining, for example.
• Ridges 58 and flats 60 extend longitudinally along core 36 and resist relative movement, such as relative rotational movement, between core 36 and polymer matrix layer 38 responsive to torsional and/or other types of loading which may be imposed upon core 36 as described above.

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• Health & Medical Sciences (AREA)
• Orthopedic Medicine & Surgery (AREA)
• Cardiology (AREA)
• Oral & Maxillofacial Surgery (AREA)
• Transplantation (AREA)
• Engineering & Computer Science (AREA)
• Biomedical Technology (AREA)
• Heart & Thoracic Surgery (AREA)
• Vascular Medicine (AREA)
• Life Sciences & Earth Sciences (AREA)
• Animal Behavior & Ethology (AREA)
• General Health & Medical Sciences (AREA)
• Public Health (AREA)
• Veterinary Medicine (AREA)
• Prostheses (AREA)

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• 2006
  • 2006-02-14 JP JP2007556232A patent/JP4773465B2/ja not_active Expired - Fee Related
  • 2006-02-14 WO PCT/US2006/005089 patent/WO2006091423A2/en active Application Filing
  • 2006-02-14 US US11/353,392 patent/US10070961B2/en active Active
  • 2006-02-14 CA CA2598177A patent/CA2598177C/en not_active Expired - Fee Related
  • 2006-02-14 EP EP06734971A patent/EP1855625A2/de not_active Withdrawn

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